Abstract: In order to avoid introducing non-combustible reagents during the valence adjustments of Pu in the Purex process for nuclear fuel reprocessing, a new catalytic oxidation technology for conversion of Pu(Ⅲ) to Pu(Ⅳ) was studied in this paper. The influence of temperature, nitric acid concentration, and hydrazine concentration on the completeness and kinetics of Pt-catalyzed oxidation of Pu(Ⅲ) was investigated. The experimental results show that in the presence of a platinum gauze catalyst Pu(Ⅲ) in a hydrazine-containing solution can be quickly and almost quantitatively (>99.9%) oxidized to Pu(Ⅳ) at 70℃ and nitric acid concentrations higher than 3 mol/L. The increase of HNO₃ concentration and elevation of temperature favores the oxidation of Pu(Ⅲ). The concentration of hydrazine also shows some influence: the higher the concentration of hydrazine is, the longer the induction period will be.